JP2022509312A - Drum brake - Google Patents

Abstract

In particular, in order to control the electromechanically operable brake of the automatic compensating brake type, it is necessary to sense the force acting on the abutment (6) of the brake shoes (2, 3). The abutment (6) is therefore formed from a solid material that deforms under load and provides a measuring device that senses this deformation. The shape of the abutment (6) is selected so that the abutment has a measurement gap, and the size of the measurement gap changes as the abutment is loaded. The size of the measurement gap can be sensed, for example, by a Hall sensor or an AMR sensor.

Description

The present invention relates to a drum brake having a servo type structure having a brake drum and two brake shoes. The two brake shoes can be attached to the brake drum, and the drum brake is arranged on the brake shoe side of the carrier plate, respectively. Has a pressure end and a support end, there is an expansion device between the pressure ends, the expansion device is mounted so that it floats against the carrier plate, and pressure is applied to the two pressure ends. Supported at the force introduction point at the end, there is a ram between the support ends, the ram is mounted floating relative to the carrier plate and supported on two support ends to transmit the force.

This type of electrically operable drum brake, in which the expansion device consists of an electric actuator, is described in International Publication No. 99/53214 A1 pamphlet.

Information about the amount of force acting on the drum brakes is needed to be able to control or adjust the actuator when applying braking. According to International Publication No. 99/53214 A1 pamphlet, a load sensor is placed on the end face of the abutment to measure the force on which one of the brake shoes rests on the abutment.

However, this information is not accurate enough to control or adjust the electric actuator. This is because the frictional forces acting on the brake shoes when applying braking may differ, and therefore the bearing forces affected by the frictional forces may also vary from brake shoe to brake shoe. Therefore, this bearing capacity of the brake shoe does not accurately reflect the total amount of force and braking torque acting on the drum brake.

Therefore, the present invention is based on the object of creating a drum brake with a load measuring device on the abutment that reflects the total amount of force acting on the drum brake when braking is applied.

To this end, the following are provided: each brake shoe has a pressure head at its pressure end adjacent to the force introduction point, and both pressure heads are between them. Being supportable on an abutment placed in and connected to a carrier plate, and that the abutment as a whole is embodied as a mass component that is elastically deformable under load. It is proposed that one or more sensors be provided that detect the deformation of the abutment that occurs under load in order to allow the braking torque generated by the drum brake to be determined by the sensor signal.

This configuration of the abutment makes it possible to determine the braking force of a drum brake with a servo type structure.

A strain gauge attached to the abutment can be used to determine the deformation of the abutment.

To achieve a clear deformation, the abutment is preferably formed by a base connected via a web to a pedestal tightly connected to the carrier plate, with the pressure head leaning against both edges of the base. When the base is exposed to a load, the base is displaced or tilted with respect to the pedestal, which can be detected by measurement.

In a first simple embodiment, the base is connected to the pedestal via a central web, and the facing edges of the base and pedestal extend parallel to each other and surround the measurement gap between them. As the base moves relative to the pedestal, the size of the measurement gap changes. Changes in the size of the measurement gap can be detected by measurement.

Another embodiment assumes that the abutment has a U-shape with a base and two arms, the two arms projecting from the base, on the outside of which the abutment end of the brake shoe is supported, 1 One or more sensors are of the type capable of detecting the tilt of the arm changing under load.

For this purpose, the base is supported by a central web originating from a pedestal fixed to the carrier plate and adjacent to the inner edge of the base, so that the arm is directed towards the carrier plate.

In order to form a measurement gap in this embodiment as well, the present invention assumes that a pin projecting laterally from the central web reaches the inner edge of the arm while forming a measurement gap.

In another embodiment of the abutment, the base and pedestal are connected to each other via two struts located at the edges to form a frame, with at least one pin originating from the pedestal extending to the inner edge of the base. It is assumed that a measurement gap is formed.

For unidirectional loads, the rectangular frame is bent into a parallelogram, resulting in a proportional reduction in the measurement gap.

To improve measurement accuracy, the pedestal, web, and base are preferably designed as an integral component.

As already explained above, the measurement of abutment deformation can be performed with the help of strain gauges.

The determination of the measurement gap size can be performed, for example, by a Hall sensor or an AMR sensor based on the anisotropic magnetoresistive effect, for which purpose the arm is a magnet that acts as a signal transmitter for the Hall sensor or AMR sensor. It is equipped with.

Hereinafter, the present invention will be described in more detail based on three exemplary embodiments. The drawings show:

A brake drum comprising a first embodiment of an abutment. An enlarged view of the abutment of the drum brake shown in FIG. Enlarged view of the second embodiment of the abutment. Enlarged view of the third embodiment of the abutment.

FIG. 1 is a perspective view of an automobile drum brake, wherein the drum brake includes a circular carrier plate 1 and two brake shoes 2 and 3 arranged concentrically with respect to the central axis of the carrier plate 1. ..

Brake shoes 2 and 3 are concentrically surrounded by brake drums (not shown here), the brake drums are connected to the wheels of the car to be braked, and brake shoes 2 and 3 are pressed against the brake drums. When this is done, the rotating wheel slows down (regular brake) or the stationary wheel is prevented from rotating (parking brake).

The brake shoes 2 and 3 each have a pressure end and a support end, and an expansion device 4 is arranged between the opposing pressure ends. This is usually a hydraulic, electromechanical, or electrohydraulic actuable device.

Similarly, there is a ram 5 between the opposite support ends, which transfers force from one brake shoe to the other brake shoe.

Both the expansion device 4 and the ram 5 are mounted so as to float in the circumferential direction with respect to the carrier plate 1, so that this is a "duoservo" brake with a strong automatic compensating effect.

An abutment 6 is provided to support a braking force acting as a frictional force between the brake shoes 2 and 3 and the brake drum. It is located radially outside the expansion device 4, where pressure heads 7 and 8 are present adjacent to the force introduction point of the expansion device 4 and further at the ends of the brake shoes 2 and 3. These are supported on both sides of the abutment 6. Since both the expansion device 4 and the ram 5 are mounted so as to float, the braking force is transmitted only from the trailing brake shoe to the abutment 6 in each case.

Considering the case where the brake drum rotates counterclockwise according to the arrow 9 shown, the brake shoe 2 shown on the left side is the leading brake shoe, and the brake shoe 3 shown on the right side is the trailing shoe. Is.

The expansion device 4 pushes open the two brake shoes 2 and 3, and the leading brake shoe 2 is carried by the brake drum in the direction of rotation with respect to the carrier plate 1. The frictional force exerted on it is also transmitted by the ram 5 to the trailing brake shoe 3, so that the pressure head 8 is supported on the abutment 6.

Here the invention assumes that bearing capacity is measured there, which force represents a measured value of braking force and can therefore be used to control the expansion device 4.

For this purpose, in the simplest case, the abutment 6 shown in FIG. 2 consists of a mass but flat component that projects vertically from the carrier plate 1 and is secured to it, thus the pressure head 7, the pressure head 7. Allows 8 to rest on its edge facing the circumferential direction.

Here, the abutment 6 comprises a pedestal 10, and it is the base 12 that is connected to the pedestal 10 via the narrow central web 11, with respect to its circumferentially facing edges, the brake shoes 2, 3 pressure heads 7 and 8 can be arranged. Since the facing edges of the pedestal 10 and the base 12 extend parallel to each other with a small gap, two measurement gaps 13 and 14 are formed between the pedestal 10 and the base 12 starting from the web 11. ..

When the brake drum is rotated counterclockwise according to the arrow 9 shown, the brake shoe 2 shown on the left is the leading brake shoe and the one shown on the right is the trailing brake shoe 3. Due to the frictional force between the brake shoe and the brake drum, the brake shoe is mounted so that it floats and is carried in the direction of rotation, so that the trailing brake shoe 3 is supported on the base 12 of the abutment 6. The base is tilted relative to the pedestal 10, so that the measurement gap 14 facing it widens and then the outwardly facing measurement gap 13 narrows, as shown in FIG.

These changes can be detected by appropriate sensors and represent the value of the introduced braking force, which can then be used to control the expansion device.

When the directions of rotation are different, the functions of the two brake shoes 2 and 3 are reversed, the left brake shoe becomes the trailing shoe, the right brake shoe becomes the leading shoe, and as a result, the latter becomes the abutment 6. It is supported on the base 12, so that the measurement gap 13 on the left side facing it widens and then the measurement gap 14 on the right side facing outwards narrows.

Another possibility of abutment design is shown in FIG. Extending from the pedestal 10 fixed to the carrier plate 1 is the central web 16, which joins the lateral web 17, and each arm 18 directed at the pedestal 10 from each of its ends. , 19 extends. Therefore, the central web 16, the lateral web 17, and the two arms 18 and 19 form a T. The pressure heads 7 and 8 of the brake shoes 2 and 3 are arranged with respect to the outer edges of the arms 18 and 19 facing in the circumferential direction.

Laterally projecting from the central web 16 are two pins 20 and 21, which terminate just before the inner edge of the arms 18 and 19 to form measurement gaps 13 and 14 in each case. There is.

Each leading brake shoe 2, 3 bends the arm 19 or 18 on which it is supported inward, so that the associated measurement gap 14 or 13 is reduced in size, which can be detected by measurement. ..

At the same time, the pins 20 and 21 function as an overload protection device. If the braking force becomes too great, the arms 17 and 18 will be supported by the associated pins 20 and 21.

A third embodiment shown in FIG. 4 comprises a pedestal 10 and a base 12, which are connected to each other via two struts 22 and 23 located at the two edges and thus have a central opening. Form a frame. Extending from the inner edge of the pedestal 10 separating the openings are two pins 20, 21 which extend to the inner edge of the base 12, leaving measurement gaps 13 and 14.

When the base 12 is loaded in the circumferential direction, it is displaced parallel to the pedestal 10, resulting in a rectangular frame deforming into a parallelogram, where the base 12 is the pedestal 10 and the pins 20 and 21. Closer to the end, as a result, the measurement gaps 13 and 14 are correspondingly reduced in size.

In all embodiments, there are various possibilities available for measuring changes in the measurement gap. A sensor that uses the anisotropic magnetoresistive effect (AMR effect), or an alternative, a linear Hall sensor can be used.

Regardless of the measurement of the measurement gap size, each change in the shape of the abutment can be detected by a strain gauge.

The sensor makes it possible to measure the braking torque acting on the drum brake. It is used to control the braking effect of the drum brake.

1 Carrier plate 2 Brake shoe 3 Brake shoe 4 Expansion device 5 Ram 6 Abutment 7 Pressure head 8 Pressure head 9 Arrow 10 Pedestal 11 Web 12 Base 13 Measurement gap 14 Measurement gap 16 Central web 17 Lateral web 18 Arm 19 Arm 20 pin 21 Pin 22 Supports located at the edge 23 Supports located at the edge

Claims (10)

A drum brake having a servo type structure having a brake drum and two brake shoes (2, 3), the two brake shoes (2, 3) can be attached to the brake drum, and the drum brake is a carrier. Arranged on the brake shoe side of the plate (1), each has a pressure end and a support end, an expansion device (4) exists between the pressure ends, and the expansion device (4) is the carrier plate. Attached so as to float relative to (1), it is supported at the force introduction point at the pressure end to introduce force to the two pressure ends, and there is a ram (5) between the support ends. , The ram (5) is a drum brake that is attached so as to float with respect to the carrier plate (1) and is supported on the two support ends in order to transmit a force, and each brake shoe (2). 3) has a pressure head adjacent to the force introduction point at its pressure end, both pressure heads (7, 8) located between them and on the carrier plate (1). It is supportable on the connected abutment (6), and the abutment (6) as a whole is embodied as a mass component that is elastically deformable under load. To allow the braking torque generated by the drum brake to be determined by a sensor signal, one or more sensors are provided that detect the deformation of the abutment (6) that occurs under load. Drum brake featuring. The abutment (6) is formed by a base terminated by a pedestal (10) tightly connected to the carrier plate (1) via a web (11) and the pressure heads (7, 8) are the base. The drum brake according to claim 1, wherein the drum brake leans against both edges of (12). The base (12) is connected to the pedestal (10) via a central web (16), and the opposing edges of the base (12) and the pedestal (10) extend parallel to each other and between them. 2. The drum brake according to claim 2, which surrounds the measurement gap of. The abutment (6) has a U-shape with a base (12) and two arms (18, 19), the two arms (18, 19) projecting from the base and the pressure head at its outer edge. It is characterized in that it can support (7, 8) and that the one or more sensors are of a type capable of detecting the tilt of the arm (18, 19) changing under load. , The drum brake according to claim 2. The base (12) is supported by a central web (20) originating from a pedestal fixed to the carrier plate (1) and adjacent to the inner edge of the base (10), resulting in the arms (11, 12). ) Is the drum brake according to any one of claims 1 to 4, wherein the drum brake is directed toward the carrier plate (1). Claim 4 or 5, characterized in that a pin (20, 21) laterally projecting from the central web (16) reaches the inner edge of the arm (18, 19) while forming a measurement gap. The described drum brake. The base and the pedestal are connected to each other via two struts (22, 23) located at their edges to form a frame, and at least one pin originating from the pedestal is the base (12). The drum brake according to claim 5, wherein the drum brake extends to the inner edge of the surface to form a measurement gap. The drum brake according to claim 5, wherein the pedestal (10), the web (20), and the base (12) form an integral component. The drum brake according to any one of claims 1 to 8, wherein a strain gauge is attached to the abutment (6) in order to detect deformation of the abutment (6). The drum according to any one of claims 1 to 8, wherein a sensor based on the anisotropic magnetoresistive effect or the Hall effect is used to detect the deformation of the abutment (6). break.

Images